Well, I have to say "Yes" to this.
Its not a happy thought, but its true.
MGM is closed every Wednesday.
Its closed somewhere between 6:30pm and 9pm, usually at about the start time of Fantasmic!
And this park closing happens virtually every day of the week.
Every park at WDW is subject to this sad fact.
The bright spot is that they close the parks 3 hours later for WDW on-property resort guests on PM EMH nights.